Electric heater



Oct. 25, 1932. c. lPsEN E11-AL ELECTRIC HEATER Filed June 6, 1929 Tsi@ 2.

lll/111111111 Inventors; Carl L. Ipse'm, Albert N. Otis, bg 6% Them Abbor'heg.

Patented Oeazs, 1932.

(JN-fran 5121x1115 PATENT OFFICE CARL m AND ALBERT N. OTIB, l' SCHENECTADY, NEW YORK, ASSIGNORS T0 GENERAL ELECTRIC COIPANY, A CORPORATIQN 0F NEW YORK ELECTRIC HEATER Application iled June 6, 1929. Serial No. 368,898.

Our invention-relates to electric heaters and has for its object the provision of an electric heater which is simple and compact in construction and durable andeicient in operation. p v

Although it obviously has other applications, our invention is particularly use ul in connection with li uid heaters such as steam boilers and the li e.

Electric heaters particularlyadapted to steam boilers, heretofore, have been provided. One form of such an electric heater comprised a strip-like resistor formed in the shape of a hairpin, and a plurality of elec'- trically insulating, heat'refractory spacing and supporting members for the resistor. These supporting members were secured to the resistor and were shaped so that the electric heater could be slid freely into the boiler tubes. Such an electric heater is described and claimed in the United States Patent No. 1,471,913 granted to A. N. Otis and dated y AOctober 23, 1923. It has been found at times that the strip resistor when highly heated would bend or deflect laterally and in some cases would ground to the boiler tube. This was due to the fact that the ribbonresistor in expanding thermally attempted to slide or push its insulating supporting members through the tube against the relatively large frictional -forces occurring between the suppo`bring members and the inner walls of the tu It is one of thelaspects of our present invention to provide an electric heater which may be slid freely-into the boiler tube and,

rmit free exmoreover, one which will respect to 1ts pansion of the resistor wit su porting members.v

n carryin our invention into eiect in one form thereo we provide the resistor with a plurality of electrically insulating, heat refractory supports spaced longitudinally of the resistor. Each su port is provided with a passageway for -slidhbly receiving the re-` sistor, so that the resistor when heated may expand freely with respect to its supports. Moreover, we provide a spacing member for the sup orts to which the su ports will be detacha ly secured so that w en assembled with the spacing member relative longitudinal and rotative movement between them will be prevented. Preferably, the stripshaped resistor will be formed with a crimp extending longitudinally throughout its length so that the mechanical strength of the resistor is materially increased. Moreover, we prefer to shape the walls of the passage- Ways provided in the supports so as to provide for line contact between these walls and the resistor passed therethrough.

For a more complete understanding of our invention reference should be had to the accompanying drawing, in which Fig. 1 is an elevation partly in section of a portion of a steam boiler which embodies our invention; Fig. 2 is a section in plan of one of the boiler tubes provided with an electric heater formed in accordance with our invention;

Fig. 3 is a perspective' of a'portion ofou'r electric heater; Fig. 4 is an exploded view illustrating one of the resistor supporting members used in our electric heater; and Fig. 5 is an elevation of afportion of the spacing member used in our electric heater.

Referring to the drawing we have shown our invention in one form in connection with a steam boiler having a plurality of heating tubes, each of which is provided with an electric heater. As shown, the boiler com- ,u prises a cylindrical metallic shell 10 which together with the metallic head 11 provides a water and steam space 12. It will be understood that the cylindrical shell 10 will be covered' completely by a heat insulating jacket 13 made from a suitable material such as asbestos. y

The water space 12 is provided with a plurality of suitable metallic heating tubes 14 each of which is rovided with a leak proof m' joint with the liead 11 and is extended through the `Water space to. the opposite end of the boiler (not shown). Each tube 14 is provided with an electric heater 15. As shown, each heater comprises an edgewise strip-shaped resistor 16 bent or otherwise formed into a hairpin shape, and a plurality Aof electrically insulating, heat refractory spacingand supporting members 17 spaced longitudinally of the resistor. The resistor l0' will be formed 'from any suitable material i such as a nickel-chromium alloy while the electrically insulating, heat refractory supports preferably will be formed from some suitable material having a low thermal co- 1'5" It will be observed (Figs. Sand 4.) that each spacing and supporting member 17 comprises a pair of cooperating members which when assembled embrace the respective leg portions 16a, 16?) of the resistor. Thus, each support is provided with a. base portion 18 and with a cooperating head portion 19. The base member 18, as shown, is provided with a pair of sidewalls 20 and with a substantiallgy cylindrical spacing member 21 positioned between and spaced from the side walls so as to provide a recess on each side of the s acing member. The cooperating-head mem r 19 is provided with a Pair of side walls 22, which in the assembled heater Fi g.

3), cooperatel with the side walls 20' and the spacing member 21 of the base portiop so as to provide a pair of enclosed passageways, one on each side of the spacing member 21. It will be understood that these passagewa s in the assembled heater serve to receive t e respective leg portions of the hairpin shaped resistor. Thus,` in the assembled heater (Fig. 3) the resistor will be provided with a number of spaced supports in which the resistor may 'freely slide. In order to prevent relative turning or lateral movement between the two portions 18 and 19 when assembled, we provide the spacing member 21 with a projecting portion 24 of .some non-circular cross section. We have shown the member 24 vwith a square cross section.Y The member 19 is provided with an aperture 25 of corresponding cross section, so thatwhen the two members are assembled, as shown in Figs. '2 and 3, it will be impossible for either member to twist or turn with respect to the other member.

Preferably the inner surfaces of the walls 20 and 22 will be tapered towards their central portion, as indicated by the ordinal 27, so that when the strip-like resistor is assembled with the supports,'a line contact will be provided between the supports and the resistor on both sides of the resistor. This small area of contact oifers but a very small muiing effect to the radiation of heat from the reslstor and consequently there is no appreciable tendency for the resistor to overheat in spots due to the muiiiing effects of the parts in engagement with it.

In order to prevent relative, longitudinal and rotative movement between the several supporting members 17, we provide a suitable spacing member 30 to which each support will be detachably secured. As shown, the support 30. is of substantially rectangular cross section and each support is provided with a recess of corresponding form so that the member may be fitted snugly upon the spacing member. Thus, as Shown in Figs. 3 and 4, the base' member 18 is provided with a recess 31 shaped so that when assembled with the s acing member the support will be secure upon the spacing member'in such manner that any turning of the support about the member is prevented. In order to prevent longitudinal movement of the support upon the s acing member, we provide the spacing mem er with a projecting pin 32 which in the assembled heater will be received by a suitable recess 33 provided in the base member 18. In assembling the electric heater, the

base portions 1 8 Aof the supports will be y 'placed upon the'` spacing strips 30 so that the pins 32 will be received in the respective ref cesses 33 provided in the base portions. After the base portions have thus been positioned upon the spacing strip, the hairpin shaped resistor will be mounted in therecesses provided in the supports so that the spacing members 21 will lie between the leg portions of the resistor. The members 19 will then be assembled with the base portions 18 to complete the heating unit.

By reason of thev foregoing construction it will be observed that the electric heater is a self-contained unit which may be inserted'in the boiler tube. Preferably the 'supporting members will'have a cross section l substantially the same as that of the boiler tubes. Thus, as shown, the supporting ,members will be of circular cross section. Moreover, the supports will have a diameter substantially equal to the diameter of the boiler tubes so that when the heater is assembled in the tubes, there will be no possibility of the head and base members 18 and 19 being displaced. Thus these members, comprising the support, will be secured in their proper assembled positions.

It will be observed that the metallic head 11 is positioned within the cylindrical shell so as to provide a space 35 in the end portion of the boiler. In this space we provide the terminal connections for the heating units.

As'shown, the terminals of the heating unitsare connected as desired by means of electrically insulating clamps 36 which are secured to a transverse metallic supporting member A37. This member is secured to the boiler by It is to be noted that the hairpin shape iven the resistor performs' an important unction in that the heating eectper unit length of the boiler is doubled. Moreover, a Very large radiating surface is obtained by iving the resistor a strip-like form. It also 1s to be noted that by -mounting the resistor edgewise, the number of supports may be materially lessened since the mechanical strength ofthe resistor as a beam is increased materially.

l/Vhat we claim as new and desire to secure by Letters Patent of the United States uis:

1. An electric heater comprising a resistor, a plurality of electrically insulating supports for said resistor spaced atintervals longitudinally thereof, each of said .supports comprising a plurality of cooperating detachable sections arranged when assembled to. provide an inclosedpassagewa for receiving said resistor, a spacing mem er for said supports, and interlocking means between said supports and said spacing member preventing relative longitudinal and rotative movement between said spaced insulators, said interlocking means providing for removal o each support independently of the remainder.

2. An electric heater comprising a striplike resistor formed in the shape of a hairpin, a plurality of electrically insulating supports for said resistor, each of said supports comprising a pair of cooperating detachable sections arranged when assembled to recelve the lengths 'of said hairpin resistor between them and to deline sepa-rated inclosed passageways for said lengths, a strip-like member on which said supports are spaced at intervals and means on said member engaging said supports to prevent relative movement between them.

3. An electric heater comprising a stripshaped resistor formed into edgewise lengths, a plurality of electrically insulating, heat refractory supports for said resistor spaced at intervals lengthwise of said resistor, each support having a plurality of detachable sections arranged when assembled to define separated inclosed passageways embracing the respective llengths of said resistor, a spacing member for said spaced supports and interlocking means between said spacing member and said supports for preventing relative rotative and longitudinal movement between said supports.

4. An electric heating unit comprising an element of resistance material bent in the form'of a hairpin, s acing and supporting insulating members orsaid resistance element intermediate the length thereof, each of said members being provided with a plurality of detachable sections arranged when assembled to define separated inclosed passageways for embracing the respective lengths of said resistance element, and a strip to which said insulating members are detach- I freely ably secured at spaced intervals along the length thereof, said insulating members being shaped so that they together with said resistance element and said strip can be slid into an elongated heating space as a unitary structure. i

, 5. An electric heater comprising a crimped strip-'shaped resistor formed in the shape of a hairpin so to provide a pair of substantially parallel edgewise lengths, a plurality of electrically insulating, heat refractory supports for said resistor, each support having a pair of passageways for slidably receiving the respective edgewise lengths of said hairpin shaped resistor, the side walls of said passageways being shaped to provide for line contact with the side surfaces of said resistor, and means for securing said supports in lined spaced relation.

6. An electric heater comprising a resistor formed in the shape of a hairpin, and a support for said resistor, having a member provided with a pair of side Walls and a spacing v member positioned between said side walls whereby a pair of recesses are provided in said member in which the respective lengths of said hairpin shaped resistor are received with said spacing member positioned 'between them, and a second member for cooperating with said first member so that when assembled with said first member a pair of inclosed passageways are formed for the respective lengths of said i'esistor.

7. An electric heater comprising an edgewise strip resistor formed in the shape of a hairpin and a support for said resistor having a base member provided with a pair of side walls and a substantially cylindrical spacing member positioned between said side walls whereby a recess is provided on each side of said spacing member, a second member for cooperating with said base member shaped so that when assembled with said first vmember, an inclosed passageway is formed on each side of saidspacing member, said passageways beings provided to receive the respective leg portions of said hairpin-shaped resistor and having walls opposite the spacing member shaped to providefor line contact with the side surfaces of the edgewise ribbon resistor, and a member of non-circular cross section projecting from said spacing member, said second member being provided with an aperture of corresponding cross section for receiving said projecting member.

8. An electric heating unit for liquid heaters and the like provided with heating tubes, comprising a resistor and a plurality of electrically insulating supports for saidresistor, each support comprising a pair of cooperating portions which when assembled provide a passageway for slidably receiving said resistor, said portions being proportioned so prising an edgewise strip-like rcsistorformed in the shape of a hairpin, a plurality of substantially cylindrical electrically insulating, heat refractory spacing and supporting members for said resistor spaced longitudinally of said resistor whereby it can be slidably supported within the tubes of said liquid heater, and a spacing member for securing said supporting members in fixed relation with respect to each other.

10. An electric heating unit for liquid heaters and the like provided for heating tubes, comprising anA edgewise strip-like resistor formedin the shape 'of a hairpin, a plurality of insulating supports for said resistor spaced longitudinally thereof, each of said supportshaving a pair of passageways for receiving the respective leg portions of said hairpin resistor, and a spacing member for securing said supports in fixed spaced relation so that said heating unit can be slid freely into the tubes of said liquid heater and supported therein on said insulators, each of saidsupports being provided with a recessfor receiving said spacing member so that relative rotation between said supports is prevented. Y

1l. An electric heating unit for boilers and the like provided with heating tubes, comprising a strip-like resistor formed in the shape of a hairpin, a plurality of electrically insulating, heat refractory supports for said resistor spaced lonigtudinally thereof, each of said supports being provided with a pair of spaced passageways for slidably receiving the respective lengths of said hairpin resistor, and a spacing strip for said supports provided with a plurality of projecting members spaced at intervals along the length of said strip, each support being provided with i a recess for receiving one of said projecting members so that said supports are spaced at intervals along the length of said strip, and each support being shaped so that saidheater can be slid freely into the heating tubes of said boiler and supported therein on said supports. v

12. An electric heater for liquid heaters and the like provided with longitudinally arranged cylindrical heating tubes comprising a strip-like resistor formed in the shape of a hairpin, and a plurality of electrically insulating supports for said resistor spaced at intervals along the length thereof, the portions of said resistor between said supports being self-supporting, each of said supports comprising a plurality of detachable sections arranged when assembled to deaseaeer line a pair of separated inclosed passageways for slidably receiving the respective lengths of said resistor and proportioned to be tted into said, cylindrical tubes of said heater so supporting members in fixed spaced' relation so that said members together with said resistor can be slid freely as a unit into the tubes of said liquid heater and interlocking means between said supporting members and said spacing member arranged to prevent relative rotative motion between said supports.

14. An electric heater for'liquid heaters and the like provided with cylindrical heating tubes comprising a strip-like resistor formed in the shape of a hairpin, a plurality of cylindrical insulating members having diameters substantially equal to the dia-meters of said tubes for supporting said resistor spaced at intervals along its length, each supporting member comprising a plurality of sections arranged when assembled to define separated inclosed passageways for the respective lengths of said resistor and to be secured in their assembled positions by the walls of said tubes when positioned therein, a spacing member for securing said supporting members in fixed spaced relation so that said members together with said resistor can be slid freely into the tubes of -said liquid heater as a unitary structure and interlocking means between said supports and spacing member arranged to prevent relative rotative motion vbetween said supports.

In witness whereof, we have hereunto set our hand this 4th day of June, 1929.

CARL L. IPSEN. ALBERT N. OTIS. 

